To sum up (the key message of Medjugorje), we can say that Our Lady's messages underline that peace is the greatest good, and that faith, prayer, fasting and conversion are the means by which we can attain it.
Fr. Ljudevit Rupcic
Professor of Theology and translator of Sacred Scripture into the Croatian language
Fr. Rupcic is resident in Medjugorje
http://medjugorje.hr.nt4.ims.hr/News.aspx
(select English translation at bottom of text).
Peace: The peace Our Lady calls for is the peace of Christ in the soul, rather than a social or world peace. As suggested in the co-title of the website it is a "true peace", a peace that can only come from God.
Faith: In the words of Our Lady, "There is one God and one Faith. Believe firmly."
Prayer: Our Lady calls for morning and evening prayer with a length of up to three hours a day. She emphasizes the importance of the Rosary as the fundamental form of devotional prayer.
Fasting: Our Lady has requested fasting twice per week, on Wednesdays and Fridays. It needs to be done with devotion and love to be effective. An ideal fast would be "bread and water".
Penance: This is a general call to sacrifice and self-denial. From 1982, Our Lady has made a call for monthly confession.
Conversion: As Dr Mark Miravalle (see bibliography reference 2) puts it "Conversion for the believer means to turn one's heart towards God and away from sin to an ever-deepening degree, experiencing greater faith through contrition. For the unbeliever, conversion is the call to have faith in the one true God and to turn from sin through repentance".